<!--
  ****************************************************************************
  * Copyright 2018-2020,2021 Thomas E. Dickey                                *
  * Copyright 1998-2015,2017 Free Software Foundation, Inc.                  *
  *                                                                          *
  * Permission is hereby granted, free of charge, to any person obtaining a  *
  * copy of this software and associated documentation files (the            *
  * "Software"), to deal in the Software without restriction, including      *
  * without limitation the rights to use, copy, modify, merge, publish,      *
  * distribute, distribute with modifications, sublicense, and/or sell       *
  * copies of the Software, and to permit persons to whom the Software is    *
  * furnished to do so, subject to the following conditions:                 *
  *                                                                          *
  * The above copyright notice and this permission notice shall be included  *
  * in all copies or substantial portions of the Software.                   *
  *                                                                          *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS  *
  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF               *
  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.   *
  * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,   *
  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR    *
  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR    *
  * THE USE OR OTHER DEALINGS IN THE SOFTWARE.                               *
  *                                                                          *
  * Except as contained in this notice, the name(s) of the above copyright   *
  * holders shall not be used in advertising or otherwise to promote the     *
  * sale, use or other dealings in this Software without prior written       *
  * authorization.                                                           *
  ****************************************************************************
  * @Id: curs_bkgd.3x,v 1.32 2021/06/17 21:30:22 tom Exp @
-->
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
<HEAD>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="generator" content="Manpage converted by man2html - see https://invisible-island.net/scripts/readme.html#others_scripts">
<TITLE>curs_bkgd 3x</TITLE>
<link rel="author" href="mailto:bug-ncurses@gnu.org">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</HEAD>
<BODY>
<H1 class="no-header">curs_bkgd 3x</H1>
<PRE>
<STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>                                                    <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>




</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
       <STRONG>bkgdset</STRONG>,  <STRONG>wbkgdset</STRONG>,  <STRONG>bkgd</STRONG>,  <STRONG>wbkgd</STRONG>,  <STRONG>getbkgd</STRONG>  - <STRONG>curses</STRONG> window background
       manipulation routines


</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
       <STRONG>#include</STRONG> <STRONG>&lt;curses.h&gt;</STRONG>

       <STRONG>void</STRONG> <STRONG>bkgdset(chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>
       <STRONG>void</STRONG> <STRONG>wbkgdset(WINDOW</STRONG> <STRONG>*</STRONG><EM>win,</EM> <EM>chtype</EM> <EM>ch</EM><STRONG>);</STRONG>

       <STRONG>int</STRONG> <STRONG>bkgd(chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>
       <STRONG>int</STRONG> <STRONG>wbkgd(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>

       <STRONG>chtype</STRONG> <STRONG>getbkgd(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>);</STRONG>


</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>

</PRE><H3><a name="h3-bkgdset">bkgdset</a></H3><PRE>
       The <STRONG>bkgdset</STRONG> and <STRONG>wbkgdset</STRONG> routines  manipulate  the  background  of  the
       named  window.   The  window  background  is a <STRONG>chtype</STRONG> consisting of any
       combination of attributes  (i.e.,  rendition)  and  a  character.   The
       attribute part of the background is combined (OR'ed) with all non-blank
       characters that are written into the  window  with  <STRONG>waddch</STRONG>.   Both  the
       character  and  attribute parts of the background are combined with the
       blank characters.  The background becomes a property of  the  character
       and  moves  with  the character through any scrolling and insert/delete
       line/character operations.

       To the extent possible on a particular terminal, the attribute part  of
       the  background  is displayed as the graphic rendition of the character
       put on the screen.


</PRE><H3><a name="h3-bkgd">bkgd</a></H3><PRE>
       The <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> functions set the background property of the current
       or  specified  window  and  then  apply this setting to every character
       position in that window.  According to  X/Open  Curses,  it  should  do
       this:

       <STRONG>o</STRONG>   The  rendition  of  every character on the screen is changed to the
           new background rendition.

       <STRONG>o</STRONG>   Wherever the former background character appears, it is changed  to
           the new background character.

       Neither  X/Open Curses nor the SVr4 manual pages give details about the
       way the rendition of characters on the screen is updated when  <STRONG>bkgd</STRONG>  or
       <STRONG>wbkgd</STRONG> is used to change the background character.

       This  implementation,  like  SVr4 curses, does not store the background
       and window attribute contributions to each cell separately.  It updates
       the  rendition  by  comparing  the  character, non-color attributes and
       colors contained in the background.   For  each  cell  in  the  window,
       whether or not it is blank:

       <STRONG>o</STRONG>   The  library  first  compares  the <EM>character</EM>, and if it matches the
           current character part of the background, it replaces that with the
           new background character.

       <STRONG>o</STRONG>   The  library  then  checks  if the cell uses color, i.e., its color
           pair value is nonzero.  If not, it simply replaces  the  attributes
           and  color  pair  in  the  cell  with those from the new background
           character.

       <STRONG>o</STRONG>   If the cell uses color, and that matches the color in  the  current
           background, the library removes attributes which may have come from
           the current background and adds attributes from the new background.
           It  finishes  by  setting  the  cell  to use the color from the new
           background.

       <STRONG>o</STRONG>   If the cell uses color, and that does not match the  color  in  the
           current   background,   the  library  updates  only  the  non-color
           attributes, first removing those  which  may  have  come  from  the
           current  background,  and  then  adding  attributes  from  the  new
           background.

       If the background's character value is zero, a space is assumed.

       If the terminal does not support  color,  or  if  color  has  not  been
       started   with   <STRONG>start_color</STRONG>,  the  new  background  character's  color
       attribute will be ignored.


</PRE><H3><a name="h3-getbkgd">getbkgd</a></H3><PRE>
       The <STRONG>getbkgd</STRONG> function returns  the  given  window's  current  background
       character/attribute pair.


</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
       These  functions are described in the XSI Curses standard, Issue 4.  It
       specifies that <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> return  <STRONG>ERR</STRONG>  on  failure,  but  gives  no
       failure conditions.

       The  routines  <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> return the integer <STRONG>OK</STRONG>, unless the library
       has not been initialized.

       In contrast, the SVr4.0 manual says <STRONG>bkgd</STRONG> and <STRONG>wbkgd</STRONG> may return <STRONG>OK</STRONG> "or  a
       non-negative  integer  if  <STRONG>immedok</STRONG>  is set", which refers to the return
       value from <STRONG>wrefresh</STRONG> (used to implement the immediate repainting).   The
       SVr4  curses  <STRONG>wrefresh</STRONG>  returns the number of characters written to the
       screen during the refresh.  This implementation does not do that.


</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
       Note that <STRONG>bkgdset</STRONG> and <STRONG>bkgd</STRONG> may be macros.

       X/Open Curses mentions that the character part of the  background  must
       be  a  single-byte  value.   This  implementation, like SVr4, checks to
       ensure that, and will reuse the old background character if  the  check
       fails.


</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
       These  functions  are  described  in  the  XSI Curses standard, Issue 4
       (X/Open Curses).


</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
       <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_addch.3x.html">curs_addch(3x)</A></STRONG>, <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>, <STRONG><A HREF="curs_outopts.3x.html">curs_outopts(3x)</A></STRONG>



                                                                 <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<li><a href="#h2-NAME">NAME</a></li>
<li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
<ul>
<li><a href="#h3-bkgdset">bkgdset</a></li>
<li><a href="#h3-bkgd">bkgd</a></li>
<li><a href="#h3-getbkgd">getbkgd</a></li>
</ul>
</li>
<li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
<li><a href="#h2-NOTES">NOTES</a></li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
</ul>
</div>
</BODY>
</HTML>
